The present invention relates to a secondary short preventing mechanism of a fuse to be used in an electric circuit of an automobile or the like, and particularly relates to a secondary short preventing mechanism of a fuse which is improved to prevent generation of secondary short of the fuse caused by mutual contact between holding portions for holding a fusing portion after the fusing portion has been fused.
Referring to FIGS. 8, 9 and 10, description will be made as to the schematic configuration of an ordinary fuse to be applied to a connector for connecting a wire harness of an automobile or the like. A fuse 50 is constituted by a fusible link 51 which is formed into a predetermined shape, and an insulation housing 61 in which the fusible link 51 is incorporated and which is to be removably attached onto a high density multielectrode connector (not shown) so as to make terminal connection possible.
The fusible link 51 has a pair of female terminal portions 52 and 52 facing to each other. Lock portions 53 are cut up in the female terminal portions 52 at their not-facing surface sides. Holding portions 54 having relatively narrow widths and extending upward from the not-facing surface sides respectively are bent so as to be connected to each other, and a fusing portion 55 which has a width set narrow correspondingly to a permissible fusing capacity is formed on an intermediate portion of the connection portion.
In order to receive the female terminal portions 52, the housing 61 is partitioned by an insulation partition 64 so as to form a pair of terminal receiving portions 62 and 62 and lock ditches 65 for locking lock portions 53 respectively, at lower-half portion of a space defined by a pair of inner wall surfaces facing each other. Each of the terminal receiving portions 62 has a male terminal insertion opening 63.
Further, a pair of guide ditches 67 and 67 each having a projected end portion formed with a sloping surface 67a so as to guide the lock portion 53 in a fusing chamber 66 are formed in the upper-half portion side defined by the inner wall surfaces, and a cover member 68 is fitted on an upper opening 68.
Incorporation of the fusible link 51 into the housing 61 is performed such that the lock portions 53 of the fusible link 51 are pushed, from the upper opening side of the housing 61, along the guide ditches 67 by using a suitable insertion jig or the like so as to incorporate the fusible link 51 into the housing 61. That is, by the thus pushing-in operation, the pair of female terminal portions 52 and 52 are disposed in the corresponding terminal receiving portions 62 with correct postures.
Next, the lock portions 53 are urged and energized inward by the sloping surfaces 67a respectively with advance of the insertion operation. Thereafter, at a point of time when the respective female terminal portions 52 have been received in the terminal receiving portions 62, the respective lock portions 53 are recovered from the urged state, and locked in the lock ditches 65 respectively, so that the incorporation is completed.
In the thus configured fuse 50, the respective female terminal portions 52 are fitted, through the insertion openings 63, onto male terminal portions projected in an attachment portion of a high density multielectrode connector (not shown). When an electric current over an allowable value flows in an associated circuit in this state of use, the fusing portion 55 is fused by Joule heat to thereby open the circuit so as to secure the safety of the circuit.
In the case of the foregoing conventional fuse 50, however, there is such a possibility that when the fuse 50 is used in a place such as an automobile or the like where extremely violent vibrations, shocks, or the like are generated, the support portions 54 which have lost support because of fusing of the fusing portion 55 are mutually inclined inside due to the vibrations, shocks, or the like after the fusing portion 55 has been fused as shown in FIG. 10, and the support portions 54 come into contact with each other again in a gap between portions "a" and "b" in FIG. 10. Therefore, the support portions 54 come into contact with each other to thereby generate a secondary short accident.
In order to prevent generation of such a secondary short accident, there has been proposed such a fuse as disclosed in Japanese Utility Model Unexamined Publication No. Sho. 64-33146. In the secondary short preventing structure with respective to this fuse, however, the configuration is relatively complicated and there are problems in reliability and in cost.